In image display devices such as cathode ray tube displays (CRT), liquid crystal displays (LCD), plasma displays (PDP), electroluminescence displays (ELD), and field emission displays (FED), image display surfaces are required to reduce the reflection of light from outside for improvement of visibility. A general method for improving the visibility is using an antireflection film containing an antireflection layer as a light-transmitting substrate to reduce the reflection on the display surface of an image display device.
Conventional antireflection films are known to contain, on the outermost surface, a low-refractive-index layer with a lower refractive index than a light-transmitting substrate.
Such low-refractive-index layers are required to have a low refractive index to improve the antireflection performance of the antireflection film, a high hardness and a slip property to prevent scratches so as to be mounted on the outermost surface of the film, and excellent optical properties such as transparency.
One example of antireflection films containing a low-refractive-index layer on the outermost surface is disclosed in Patent Literature 1. This antireflection film contains a low-refractive-index layer including hollow silica particles inside, which is formed from a coating solution including hollow silica particles, a binder resin such as acrylate, and the like.
As image display devices are required to have a quite high display quality, the antireflection performance of antireflection films is recently required to achieve a higher level.
However, conventional antireflection films containing a low-refractive-index layer with hollow silica particles cannot achieve sufficient antireflection performance corresponding to the recent high display quality.
Patent Literature 2 and the like disclose methods for adding a fluorine atom-containing polymer or monomer to a material for low-refractive-index layer, for example.
The fluorine atom-containing polymer or monomer has a lower refractive index than, for example, a binder resin shown in Patent Literature 1. However, a low-refractive-index layer formed from such a composition cannot achieve a sufficiently low refractive index. If the amount of the fluorine atom-containing polymer or monomer is increased so that a sufficiently low refractive index is achieved, the hardness of the low-refractive-index layer problematically decreases.
Patent Literatures 3, 4, and 5 disclose antireflection films that contain a low-refractive-index layer including a fluoropolymer and hollow silica particles.
Such a low-refractive-index layer including a fluoropolymer and hollow silica particles can achieve a lower refractive index.
However, even in the case of using such a low-refractive-index layer including a fluoropolymer and hollow silica particles, sufficient increase in the amount of the fluoropolymer to reduce the refractive index problematically causes an insufficient hardness of the low-refractive-index layer.
Thus, antireflection films are required to contain a low-refractive-index layer with a sufficient surface hardness and a lower refractive index, and to exert high antireflection performance.
In addition, such an antireflection film is required to have an excellent slip property because it is normally mounted on the outermost surface of an image display device.